Reactive ion etching (RIE) has been employed in a wide range of fields such as semiconductor fabrication, MEMS (microelectromechanical systems), and refractive x-ray optics with a large investment put towards the development of deep RIE. Due to the intrinsic differing chemistries related to reactivity, ion bombardment, and passivation of materials, the development of recipes for new materials or material systems can require intense effort and resources. For silicon in particular, methods have been developed to provide reliable anisotropic profiles with good dimensional control and high aspect ratios, high etch rates, and excellent material to mask etch selectivity (Ranganathan, N., Lee, D. Y., Ebin, L., Balasubramanian, N., Prasad, K., Pey, K. L., “The development of a tapered silicon micro-micromachining process for 3D microsystems packaging”, J. Micromech. Microeng. 18, 115028-1-8 (2008); de Boer, M. J., Gardeniers, J. G. E., Jansen, H. V., Smulders, E., Gilde, M.-J., Roelofs, G., Sasserath, J. N., Elwenspoek, M., “Guidelines for Etching Silicon MEMS Structures Using Fluorine High-Density Plasmas at Cryogenic Temperatures”, J. Micromech. Syst. 11 (4), 385-401 (2002); and Wells, T., El-Gomati, M., Wood, J., Johnson, S., “Low temperature reactive ion etching of silicon with SF6/O2 plasmas”, 9th Int. Vacuum Microelectronics Conf., 349-353 (1996).
Cl2/O2 chemistry has been studied and developed by the scientific community. See for example, Tabara, S., et al., WSi2/Poly-Si Gate Etching Using a TiON Hard Mask”, Jpn. J. Appl. Phys., Vol. 37 (1998), pp. 2354-2358.
A polymerization step has been already been used in different processes to improve anisotropy. However, they are two-step processes or contain multiple successive steps into the process (like in the Bosch process). Multi-step processes are less desirable as the sidewall profile is “scalloped” in most cases.
A multilayer Laue lens is an x-ray focusing optic, which is produced by depositing many layers of two materials with differing electron density in a particular stacking sequence where each layer in the stack satisfies the Fresnel zone plate law (Kang, H. C., Maser, J., Stephenson, G. B., Liu, C., Conley, R., Macrander, A. T., Vogt, S., “Nanometer Linear Focusing of Hard X Rays by a Multilayer Laue Lens”, Phys. Rev. Lett. 96, 127401-1-4 (2006)). When this stack is sectioned to allow side-illumination with radiation, the diffracted exiting radiation will constructively interfere at the focal point. Since the first MLLs were developed at Argonne National Laboratory in the USA in 2006 (“Multilayer Laue lenses as high-resolution x-ray optics”, J. Maser, G. B. Stephenson, S. Vogt, W. Yun, A. Macrander, H. C. Kang, C. Liu, and R. Conley, Proc. SPIE 5539, pp. 185-194 (2004)), there have been published reports of MLL development efforts in Japan (Koyama, T., Ichimaru, S., Tsuji, T., Takano, H., Kagoshima, Y., Ohchi, T., Takenaka, H., “Optical Properties of MoSi2/Si Multilayer Laue Lens as Nanometer X-ray Focusing Device”, Appl. Phys. Express 1, 117003-1-3 (2008)), and, very recently, also in Germany (Liese, T., Radisch, V., Krebs, H-U, “Fabrication of multilayer Laue lenses by a combination of pulsed laser deposition and focused ion beam”, Rev. Sci. Instrum. 81, 073710-1-4 (2010)).
The traditional technique for sectioning multilayer Laue lens (MLL) involves mechanical sectioning and polishing, which is labor intensive and can induce delamination or structure damage and thereby reduce yield (Kang, H. C., Stephenson, G. B., Liu, C., Conley, R., Khachatryan, R., Wieczorek, M., Macrander, A. T., Yan, H., Maser, J., Hiller, J., Koritala, R., “Sectioning of multilayers to make a multilayer Laue lens”, Rev. Sci. Instr. 78, 046103-1-3 (2007)). If a non-mechanical technique can be used to section MLL, it may be possible to greatly shorten the fabrication cycle, create more usable optics from the same amount of as-grown multilayer, and perhaps develop more advanced structures to provide greater stability or flexibility. Plasma etching of high aspect-ratio multilayer structures may also expand the scope for other types of optics fabrication (such as gratings, zone plates, and so-on). However, well-performing reactive ion etching recipes have been developed for only a small number of materials, and even less recipes exist for concurrent etching of more than one element so a fully material specific process needs to be developed. Further, the techniques are limited with respect to the shapes of the device to be produced,
Accordingly, it is an objective to provide sectioning of monolayers and multilayers that overcomes the problems in the art. Another goal is to demonstrate the feasibility of this technique, achievement of a uniform anisotropic etch profile (high quality profile), high anisotropy, adequate sidewall roughness control and high etching rates for thicknesses from the nanometer scale to tens of microns and in any suitably shaped multi-mono-layers.